Grad P-IE: Chemical Ecology and Host-Plant Resistance
Evaluation of inducible defense mechanisms of annual bluegrass (Poa annua) and creeping bentgrass (Agrostis stolonifera) in response to annual bluegrass weevil (Listronotus maculicollis) herbivory
Monday, November 14, 2022
11:30 AM – 11:42 AM PT
Location: Vancouver Convention Centre, Meeting Room 110
Pennsylvania State University University Park, Pennsylvania
The annual bluegrass weevil (Listronotus maculicollis)(ABW) is the most devasting insect pest of short-mown annual bluegrass (Poa annua L.) and creeping bentgrass (Agrostis stolonifera), the two predominant turfgrasses on golf courses in eastern North America. Larvae are stem borers during their first three instars, though transition to feed externally on the crown during 4th and 5th instars. Creeping bentgrass has been observed to be more tolerant to ABW herbivory, though underlying mechanisms have not been investigated. We hypothesized that creeping bentgrass elicits an inducible defense response to ABW herbivory resulting in reduced larval survivorship. Turfgrass cores were infested with adults to obtain uniform larval stages. Foliar, stem and root tissue samples were collected at three development stages (2nd, 3rd, 4th instars) to measure defense response over time. In the absence of larvae, no differences were detected in levels of jasmonic acid (JA), a phytohormone elicited by chewing insects, between turfgrasses. Salicylic acid (SA), a phytohormone associated with piercing-sucking insect feeding and plant pathogen infection, was significantly higher in annual bluegrass foliar and stem tissue compared to creeping bentgrass. Once challenged with larvae, SA only increased in annual bluegrass foliar and stem tissue compared to plants without larval feeding. No significant differences were found in either JA or SA production with ABW development from 2nd to 4th instar for either turfgrass species or tissue type. These findings suggest that defense phytohormones may play role in annual bluegrass susceptibility to ABW herbivory, but unlikely to provide resistance in creeping bentgrass.